Currently, in X-ray image diagnosis, an absorption image capturing attenuation of an X-ray after transmission through an object is used. Meanwhile, X-rays are one type of electromagnetic waves; therefore, in recent years, attention has been given to their wave nature, and attempts have been made to produce an image of a phase shift of an X-ray after transmission through an object. Such attenuation and phase shift are referred to as “absorption contrast” and “phase contrast”, respectively. An imaging technology utilizing this phase contrast has a higher sensitivity to light elements than a conventional technology utilizing absorption contrast and is thus believed to be highly sensitive to human soft tissues containing a large amount of light elements.
However, a conventional phase contrast imaging technology requires the use of a synchrotron X-ray source and a microfocus X-ray tube, and the former entails a large-scale facility while the latter cannot secure an X-ray dose sufficient for photographing a human body; therefore, it has been considered difficult to put such a conventional phase contrast imaging technology to practical use at general medical facilities.
In order to solve these problems, X-ray image diagnosis (Talbot system) which employs an X-ray Talbot-Lau interferometer that is capable of acquiring a phase contrast image with the use of an X-ray source conventionally used in medical practice is expected.
As illustrated in FIG. 5, a Talbot-Lau interferometer has a G0 lattice, a G1 lattice and a G2 lattice that are each arranged between a medical X-ray tube and an FPD, and visualizes refraction of an X-ray caused by a subject as moiré fringes. An X-ray is irradiated in a longitudinal direction from an X-ray source arranged in an upper part, and the X-ray reaches an image detector through the G0 lattice, the subject, the G1 lattice, and the G2 lattice.
As a method of producing a lattice, for example, a method in which a silicon wafer having high X-ray transparency is etched to form lattice-form recesses and these recesses are subsequently filled with a heavy metal having excellent X-ray shielding properties is known.
However, in this method, it is difficult to increase the area due to, for example, the size of available silicon wafer and restrictions on an etching device, and the imaging subject is thus limited to a small part. In addition, since not only it is not easy to form deep recesses on a silicon wafer by etching but also it is hard to evenly fill a metal into deep parts of the recesses, it is difficult to produce a lattice having a thickness enough to sufficiently shield X-rays. For this reason, particularly under high-voltage photographing conditions, a favorable image cannot be obtained due to transmission of X-rays through a lattice.
In view of the above, the scintillators, which are scintillators imparted with a lattice function and emit light in a slit form, are drawing attention.
For example, Patent Document 1 discloses a radiation detection device in which a substrate having partition walls formed on its surface and a photodetector face with each other, wherein cells divided by the partition walls are formed in a space between the substrate and the photodetector, the cells are filled with a phosphor, light-detecting pixels are arranged on the surface of the photodetector that is not in contact with the partition walls, and an adhesive layer is formed between the partition walls and the phosphor, and the photodetector. In Patent Document 1, it is disclosed that the radiation detection device satisfies a relationship of λ2≥λ1≥λ3, wherein λ1, λ2 and λ3 represent the average refractive index of the phosphor, that of the light-detecting pixels and that of the adhesive layer, respectively.
Further, Patent Document 2 discloses a scintillator panel including: a plate-form substrate; partition walls arranged on the substrate; and a scintillator layer filled in cells divided by the partition walls, wherein the partition walls are constituted by a material containing a low-melting-point glass as a main component and the scintillator layer is composed of a phosphor and a binder resin. In Patent Document 2, it is disclosed that the refractive index Np of the phosphor and the refractive index Nb of the binder resin satisfy a relationship of −0.3<Np−Nb<0.8, i.e., these refractive index values are close to each other.
In Patent Documents 1 and 2, however, no attention is given to the effective use of the partition walls as a light transmission path.